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EVOLUTION
The Evolution of a Hairstyle
19201900 1940
The Evolution of Hairstyles Continued
1960 1980 2000
Hairstyle of the Future?????
Evolution of Automobiles
1920
1916
Evolution of Automobiles
1950
1930
Evolution of Automobiles
2000
1970
Car of the Future??????
Evolution of the Cell Phone
Questions1. Can you explain how the style or product is
the same?
2. Can you explain how it changed over time?
3. What might have caused the observed changes?
4. Organisms also change over time. How is the evolution of organisms different from the evolution of styles or products?
Research on evolution
Defining Evolution
• Evolution is the theme that unifies all of the different fields of biology.
• There are many links between evolution, biodiversity, DNA and genetics.
• The modern synthetic theory of evolution combines Darwin’s basic theory of evolution by natural selectionwith the findings of population biology and genetics.
• According to this theory, evolution occurs not to individuals, but to populations.
• Evolution is a change in the allele frequency in a population’s gene pool.
***The fact that evolution occurs in populations (not individuals) is very important to your understanding of evolution.****
• Evolution is EVERYWHERE!
• Think, pair, share...
• What are some examples that you can think of?
Is Evolution a Fact?
• Fact vs. Explanation
• Evolution has occurred (e.g. fossil evidence, DNA analysis) → FACT
• Mechanism of how evolution has occurred (theory of Natural Selection) →Proposed Explanation
The “Evolution” of the Evolutionary Theory
The dynamic nature of the “evolution” of the evolution theory is an excellent vehicle with which to explore the nature of science. Many scientist contributed to the development of a theory that explained how species have transformed over time.
The “Evolution” of the Evolutionary Theory
• James Hutton (1726-1797) and Charles Lyell (1797-1875) studied the forces of wind, water, earthquakes, and volcanoes. They concluded that the Earth is very old and has changed slowly over time due to natural processes.
• Erasmus Darwin (1731-1802) suggested that competition between individuals could lead to changes in species (Charles Darwin’s grandfather)
• Jean Baptiste Lamarck (1744-1829) proposed a mechanism by which organisms change over time → that living things evolve through the inheritance of acquired characteristics.
• Thomas Malthus (1766-1834) observed that human populations cannot keep growing indefinitely. If the birth rate continued to exceed the death rate, eventually humans would run out of living space and food. Famine, disease, and war prevent endless population growth.
• Charles Darwin (1809-1882) formulated a theory of evolution by natural selection based on observations made during his voyage on the Beagle, and of selective breeding of farm animals, plants, and pets. Most famous work → On the Origin of Species by Means of Natural Selection(1859)
• Alfred Russel Wallace (1823-1913)proposed a theory of evolution by natural selection similar to Darwin’s. He wrote a paper for Darwin to review. This spurred Darwin on to agree, finally, to the release of his theory.
• In 1858, Charles Lyell presented Darwin’s 1844 essay and Wallace’s paper to the public.
• http://www.cnrs.fr/cw/dossiers/dosdarwinE/darwin.html# Darwin’s Voyage on the Beagle (watch #3, 10 and 11)
Charles Darwin:
• He was an English ____________• In_______, at the age of 22, he boarded the
____________, a ship used for scientific trips.• The vessel stopped at the
________________located in the Pacific Ocean at 1000 km from the coast of the equator.
botanist1831
HMS Beagle
Galapagos Islands
• He collected various species including 13 species of _________. These have become a key element in the formation of his final theory.
• Darwin proposed that species may change over time, and the mechanism of evolution is _____________________.
finches
Natural selection
• He wrote 2 manuscripts on these theories, but initially did not want to publish it because his ideas were ____________ and could be perceived as contradicting the religious teaching of the time. Also, he was unable to explain the origin of the variation in the populations as well as the _________________________________________________________
controversial
transmission of variations from generation to the next.
Darwin’s Theory of Natural Selection
• Overproduction: More offspring are produced by an organism than can possible survive.
• Competition: High birth rates cause a shortage of life’s necessities, leading to competition between organisms.
• Variation: Each individual differs from all other members of its species; some more than others.
• Adaptation: Variations help some organisms to be better suited to their environments than others.
• Natural Selection: The most fit (best adapted) organisms survive and reproduce.
• Speciation: New species form from ancestral species by means of natural selection.
• Variation in a species is a result ofmutations in DNA. These mutations are the source of new alleles, the variations upon which natural selection can act.
• Remember these mutations are not goal directed; they arise randomly in a population, and may produce a change in the structure or function of the organism.
• Whether or not the mutation is beneficial or harmful depends on the environment.
Evolution then selects for those organisms that are best adapted to their environment at the time.
FALSE: Others proposed that specieschanged over time.
TRUE: The body of evidence forevolution is extensive andexpanding. All observationssupport it.
FALSE: Evolution occurs in populations, not individuals.
FALSE: Evolution deals only with the origin of species.
TRUE: Evolution has been observeddirectly; there is no evidenceagainst it.
FALSE: Natural selection is the mechanism by which evolution occurs.
FALSE: Evolution is a scientificallydemonstrated fact.
FALSE: Evolution is ongoing.
TRUE: Evolution is not a random oraccidental process; there areselective aspects.
TRUE: There are no empirical observations of life, living orextinct, thatevolution cannot explain.
Survival of the Fittest
• Adaptation: is a variation that allows an organism to be better suited to its environment
• Organisms that are better adapted to their environment are more fit, thereby increasing their chance of survival and successful reproduction.
• Thus, adaptations are the result of natural selection.
• Natural Selection is the mechanism for change in a population. It occurs when organisms with favourable traits survive, reproduce and pass on their variations to the next generation.
• Tree Man- 12 lbs in strange tree like warts.
• Believed to be a mutation of the HPV virus
• Mermaid syndrome- child born with its legs fussed together making it look like a mermaid tail
• Dwarfism-individuals under 4.10’
• Over 200 known causes
• Think, pair, share
• What are some examples of adaptations?
Classification of Adaptations
1) Behavioural2) Physiological3) Structural
Adaptations can be classified in 3 ways:
Adaptation
Definition Examples
Behavioural
How organisms respond to their environment
Seasonal Migration by monarch butterflies, birds and caribou
Hibernation by bears and garter snakes
Bending of sunflowers toward the sun
Shedding of leaves in the fall by deciduous trees
Possums play “dead” to avoid predators
Bending of Sunflowers to the Sun
Grizzly Bear Hibernating
Adaptation Definition Examples
Physiological Changes in an organisms metabolic process
Antibiotic-resistant bacteria and pesticide-resistant insects
Adaptation Definition Examples
Structural Adaption of a physical feature on an animal that will increase its chance of survival
blubber helpswhales survive in the arctic waters
webbed feet help ducks to swim faster
The needles of a cactus are modified leaves that both protect the plant and reduce water loss
The Needles of a Cactus
2 Types of Structural Adaptations
• Mimicry is one type of structural adaptation that allows one species to resemble another.
• The large (up to 75 mm) _______________of the elephant hawk-moth defends itself by mimicking a snake. The swollen segments near the head contain two large “eye spots” that foolinsectivorous birds (and people) into thinking it is dangerous.
caterpillar larva
Caterpillar larvae of the elephant hawk-moth mimicking a snake
• Camouflage is another type of structuraladaptation to the appearance of organisms. Such an adaptation assists organisms to survive by allowing them to blend in with their environments.
• The stick insects resemble the shrub branchesthey inhabit.
• The stripes on tigers help them to blend in to the jungle.
Stick Insects resemble the Shrub Branches
The stripes on tigers help them to blend in to the jungle
Adaptation vs. Acclimatization
• Acclimatization is when an organism becomes accustomed to changing environmental conditions.
• It is NOT a product of natural selection
• There is NO CHANGE IN THE GENE POOL of the Species.
• For example, when the warm weather arrives after the cold of winter, we are quick to shed our winter coats and put on our short and t-shirts, even though the temp may only be at 10 degrees.
• However should a cold front sweep down from up north in the middle of summer, we dress more warmly and complain about how cold it is.
• We had become acclimatized to the warmer temps of summer
Research:You will prepare a poster (power point) describing adaptations found in a species of your choice. The poster should include the following:• the name of the species• description of the type adaptations (behavioral, physiological, structural)• an explanation of how these adaptations enables the organization to better adapt to its environment• a photo, drawing or diagram of the organism
Natural Selection Leads to Changes in Populations
There are two well-known examples in which natural selection has been observed in action.
1. H.B. Kettlewell’s study of_______________ adaptation in a population of light colouredand dark coloured pepper moths in England.
structural
Biston betularia – Salt and Peppered moth
2. The development of penicillin resistant bacteria such as Staphylococcus aureus.
• Think, pair, share....
• What does this adaptation mean for humans?
Microevolution• Describes changes that occur_______ a
population of a single species. It includes the process of natural selection, changes in allele frequencies, and changes in populations that result over time. E.g. Antibiotic-resistant bacteria
within
Macroevolution
Refers to ____________ and long-term evolutionary patterns among ______species. The evolution of new species form a common ancestor. E.g. Darwin’s Finches, origin, adaptive radiation, and extinction of the dinosaurs are examples of macroevolution.
large-scalemany
QUESTION: Does Natural Selection lead to perfection in organisms?
• No. Natural Selection operates on the variation already present in a species; it cannot create new structures or processes.
• Mutation- changes in the DNA sequence
• Natural Selection- survival of the fittest
• Genetic Drift- Shift in allelic frequenciesdue to chance events. Specifically affects small populations.
• Gene Flow- movement of individuals both in and out of a gene pool. (migration or storms)
4 Processes of Microevolution
Population Genetics
• Remember- Populations evolve NOT individuals
• How? Imagine all of a population’s genes together in a large pool called the gene pool.
• The percentage of any
specific allele in a gene
pool is called an
allelic frequency.
• When allelic frequency stays the same over a long period of time it is called genetic equilibrium.
Expanding Our Perspective
• What does Darwin’s theory of evolution mean for the wider society?
• Where is this theory applicable?
• Darwin's theory of evolution taught that species did change as a result of natural selection.
• Artificial selections- breeding plants and animals to perfection
• Social Darwinism
• Galton (Darwin’s cousin) wondered, "Could not the race of men be similarly improved?"
• Biology was destiny, perfecting the human race by, as he put it, getting rid of its "undesirables" while multiplying its "desirables"
The Effects of Disruptive, Stabilizing and Directional Natural
Selection on Variation
• Stabilizing, directional and disruptive selection are ways in which natural selection can affect genetic variation
3 Types of Selection
• Stabilizing selection- favours individuals with an average value for a trait, and selects against those with extreme variations.
• Example – Size of a newborn baby
– How many eggs in a Robins nest
• Directional selection- Favours individuals possessing values for a trait at one extreme of the distribution, and selects against the average and the other extreme. Example- Beak length in
wood peckers
• Disruptive Selection- favours individuals at both extreme ends of the distribution and selects against the average. It is also known as diversifying selection.
• Example- Limpets shell colour, dark limpets blend into the dark rocks, light coloured limpets blend into light rocks and tan limpets stand out on both surfaces.
Bean lab
Natural Selection vs. Artificial Selection
• Both natural selection and artificial selection are mechanisms of change in the gene pool of a population. The key difference is that in artificial selection, _______________individuals with the more _________ traits are allowed to reproduce. In natural selection, those individuals who are best suites to their environment _________ and _____________.
humans ensure desirable
reproduce
survive
• Artificial selection is a form of non-random mating one of the causes of change to a gene pool.
• Think, pair, share- examples of artificial selection
Examples:
- Cows that produce more milk- Fruit trees with fruit that ripen faster- Wheat crops that produce more- Horse that run faster
Where Did All the Four -Leaf Clovers Go?—Case Study
Hardy-Weinberg Principle
• The Hardy-Weinberg principle is a mathematical model that deals with the frequency of alleles in a gene pool. If the allelic frequency does not change in a population over successive generations, then evolution does not occur and the population is at equilibrium. Several conditions must be met in order to maintain this equilibrium.
Conditions for Hardy-Weinberg Principle
1.No mutation occurs so that the gene pool does not change.
2. Emigration and immigration do not occur as they would alter the gene pool.
3. The population must be large so that changes do not happen by chance alone
• All mating must be totally random so that one form of the allele is not favoured over another.
• All forms of the allele must be expressedequally so that there is no naturalselection.
• It is virtually impossible to meet these conditions, allelic frequencies do change in populations and therefore evolution does occur.
• The Hardy-Weinberg principle is also useful in explaining why genotypes within a population tend to remain the same, as well as for determining the frequency of a recessive allele.
Hardy Weinberg Principle (Examples and Calculation)
• p = frequency of the dominant allele
• q = frequency of the recessive allele
In a stable population, the frequency alleles in a population will equal to 1. This can beexpressed as p + q = 1, where
• p2 = frequency of individuals homozygous for the dominant allele
• q2 = frequency of individuals homozygous for the recessive allele
• 2pq = frequency of individuals with the heterozygous genotype
The Hardy-Weinberg principle equation (p2 + 2pq + q2 = 1) allows us to calculate the frequencies of the three genotypes, where
Steps for Solving
• 1- Convert frequency to % and solve for either q or p
• 2- using the equation 1-p=q or 1-q=p solve for the unknown
• 3- sub in the new found values of p and q into the Hardy-Weinberg Equation
• Remember to check your answer, it should add up to 1.
1. A population of mice has a gene made of 90% M alleles (black fur) and 10% m alleles(grey fur).
0. 10
0.900.010.810.18
0.01 X 500 = 5 mice with grey fur
b) if there are 500 mice in the population, how many will have grey fur?
c) If there are 500 mice in the population, how many will be homozygous for black fur?
0.81 x 500 = 405 mice homozygous for black fur
2. While studying a sample of pea plants, you find that 36 of 400 plants are short(recessive). The rest of the plants are tall.
a)Use the Hardy-Weinberg principle equation to complete the following chart.
36/400 = 0.09
0.30
0.70
(0.70)2= 0.49
2(0.70)(0.50)=0.42
a)Determine the number of heterozygous pea plants present.
a)Determine the number of homozygous tall pea plants present.
0.42 x 400 = 168 heterozygous peaplants
0.49 x 400 = 196 homozygous tall pea plants
Complete p.25-26 in your note book
How Can Genetic Variation in a Gene Pool be Altered?
1. Natural Selection: The better adapted (more fit) individuals survive and reproduce, passing on their genes to successive generations.
2. Immigration and Emigration: Adding or removing individuals from a population will affect allele frequencies and therefore gene flow.
3. Genetic Drift: The change in the gene pool of a small population due to random chance.
4. Non-random Mating: often the case as choice of mates is an important part of behavior (e.g. courtship rituals, plants self pollinate → inbreeding)
5. Mutations: occur constantly. They provide the source of new alleles, or variations upon which natural selection can take place.
2 Examples of Genetic Drift
• BOTTLENECK EFFECT → results from near extinction of a species.
• FOUNDER EFFECT → results from a small number of individuals colonizing a new area
Population Bottlenecks and Endangered Species—
Case Study
Reproductively Isolated Populations
SPECIATION occurs when members of a population become reproductively isolated from one another and can no longer interbreed to produce fertile offspring.
Factors Leading to Reproductively Isolated Populations
• When part of a population becomes geographically isolated from the parental population, allopatric speciation can occur.
Geographic Isolation -Can occur due to the formation of physical barriers
• mountains• canyons • rising sea levels• glaciers…
*Also called Allopatric speciation
Wood frog and Leopard frog have become geographically isolated -→
The physical barriers prevent gene flow between the two populations. If the different populations are subjected to different natural selection processes, allelic frequencies for genes will change.
The two populations may become so different genetically that they will no longer be able to interbreed thus they become two separate species.
• Niche Differentiation- Occurs when the gene flow between members of a population is restricted due to ecological isolation, sympatric speciation can occur.
• Some members of a population may be better adapted to a slightly different habitat in an ecosystem, and being to specialize in that habitat.
• Different selective pressures in the two habitats lead to genetic changes in the organism.
• The two populations become reproductively isolated resulting in two distinct species.
(Also called sympatric speciation)
• Alterations in Behaviour- Should a group of nocturnal mammals become active during the day, they may no longer matewith their counterparts who are active at night
• Chromosome Mutations- A malfunction in meiosis can lead to polyploidy (multiple copies of chromosomes) in a plant.
• Because plants can reproduce asexuallyand self-pollinate, the new polyploidy can reproduce, even though it is reproductively isolated from its parents
• It is estimated that between 30-80% of all plants on earth are polyploidy
• Examples include- apples, bananas, sugar cane, tobacco, wheat, peanuts, cotton….
1. Divergent Evolution (adaptive radiation)
• The process in which an ancestral species gives rise to a number of new species that are adapted to different environmental conditions.
• This process is very common on islands.
• Often occurs when a species colonizes a new environment when there are unoccupied ecological niches.
Convergent and Divergent Evolution
• The differences among homologous structures are the result of adaptation to different environments.
• For example: Darwin’s Galapagos Finches.In other cases, adaptive radiation occurred after the extinction of many other species. The rapid increase in the number of species of mammals took place after the mass extinction of the dinosaurs.
• Homologous structures refers to structural features with common evolutionary origins.
Convergent Evolution
• The process in which different organisms that live in similar distant habitats become more alike in appearance and behaviour.
• As they encounter similar environment pressures, the organisms develop analogous structures.
• Analogous structures refer to the evolution of a body parts of organisms that do not have a common evolutionary origin but are similar in function.
For example:
• Dolphins and sharks live in the water and both use their tails for propulsion. However, their tails are analogous structures with different origins. Sharks move their tails side to side, while dolphins move their tails up and down. Similarly, bat, butterfly, and bird wings are analogous structures.
Dolphin Tail
Shark Tail
Do Convergent or Divergent work sheet
Convergent or Divergent?
Convergent
Convergent
Divergent
Divergent
Convergent
Divergent
Divergent
Divergent
Divergent
Divergent
Divergent
• Vestigial Structures- Parts that seem to have no specific function in the organism, or do not contribute to increasing an organisms “fitness.”
• Think, pair, share
• What are some vestigial structures from plants, humans or animals?
Examples• Whales have small vestigial leg bones
• Emus and Ostriches have wings but cannot fly
• Humans have a coccyx or tail bone (revetments of a tail)
• Human appendix may have been left behind from plant eating ancestors
• Nipples on males
• Wisdom teeth in humans
Models of Evolutionary Change
• Gradualism- Describes the pattern of slow and gradual change over longperiods of time.
• Populations slowly diverge from one another due to differing selective pressures.
• The changes result in transitional forms that are seen in the fossil record.
Punctuated Equilibrium
• Describes the pattern of long stable periods in which species stay much the same.
• These periods were interrupted (punctuated) by short periods in which the quick pace of evolution rapidly resulted in the formation of new species.
• The stimulus for evolution is a suddensignificant change in the environment.
• The fossil records often show that rapid bursts have often followed mass extinctions. E.g. Extinction of Dinosaurs was followed by a rapid increase in mammalian species.
